1. Field of the Invention
The present invention relates to a green compact of incineration ashes of sewerage sludge and its burned product.
2. Description of the Prior Art
At present, the sewerage sludge is generally dumped out in any one of the following manners after it is once incinerated in a incinerator. Specifically,
(a) The incineration ashes of the sewerage sludge taken out of an ash hopper are, as they are or after they are added with moisture, thrown away at a reclaimed dump. PA1 (b) The incineration ashes are mixed with cement or lime, etc., granulated into particles, solidified, and finally thrown away at a reclaimed dump. PA1 (c) The incineration ashes are melted in a melting furnace, cooled, ground, and thereafter thrown away at a reclaimed dump, or utilized as an aggregate of concrete.
According to the method a), however, the volume of the incineration ashes become large per unit weight, resulting in a short span of service time of the reclaimed dump. Moreover, when the incineration ashes after they are thrown away are exposed to weather, they may be scattered into an outflow, and particularly, if the incineration ashes contain a heavy metal therein, the melting of the metal would be a cause of secondary pollution. Accordingly, the method (a) cannot be said to be suitable from the viewpoint of environmetal sanitation.
On the other hand, according to the method b), although the disadvantages of the above-described method a) are solved, it is a drawback that the total amount of the incineration ashes to be thrown away is increased by the additives mixed in the incineration ashes so that the ashes are granulated and solidified.
Meanwhile, according to the method c), since the melting furnace is required for melting the incineration ashes, a special equipment therefor is necessary, with increasing the cost for operating the equipment.
In view of the above, the present inventors have examined the character of the incineration ashes of the sewerage sludge, and noted that the incineration ashes can be easily compressed to form a solid unit by force of van der Walls under the condition of high pressure, like as general powders.